my_map.rb

#Array#map calls the passed block once for each element of the array it was called on. 
#It creates and return a new array containing the new values.

#Array#inject combines each element of an enumerator by applying the operation specified in the attached block or
#represented by an operator/method symbol (like +, -, /). If a block is specified, the block is passed an accumulator value 
#and the individual element. It then returns the value of memo.

#Array#select returns a new array containing all the elements of the passed array for which the passed block is true.

class Array


  def my_map
    new_array = []
    self.length.times do |x|
      new_array << yield(self[x])
    end
    return new_array
  end
end
end
p [1,2,3].my_map {|x| x*3}